JP6564336B2 - Non-aqueous electrolyte and non-aqueous secondary battery - Google Patents

Description

  The present invention relates to a non-aqueous electrolyte and a non-aqueous secondary battery.

  Non-aqueous secondary batteries such as lithium ion batteries are characterized by their light weight, high energy, and long life, and are widely used as power sources for various portable electronic devices. In recent years, it is also spreading for industrial use as typified by power tools such as electric tools; in-vehicle use for electric vehicles and electric bicycles. Furthermore, it has been attracting attention in the field of power storage such as a residential power storage system.

  It is desirable from a practical point of view to use a non-aqueous electrolyte as the electrolyte for a room temperature operation type lithium ion battery. For example, a combination of a high dielectric solvent such as a cyclic carbonate and a low viscosity solvent such as a lower chain carbonate is exemplified as a general solvent. Moreover, it is desirable to use an additive for the purpose of suppressing the reductive decomposition of the electrolyte solution in the negative electrode, and it has already been recognized as common sense.

For example, Patent Document 1 reports a technique for strongly forming a protective film called SEI (Solid Electrolyte Interface) on the negative electrode surface by electrochemically reacting vinylene carbonate. Patent Document 2 and Patent Document 3 report a technique for promoting SEI formation by adding lithium bis (oxalato) borate represented by LiB (C ₂ O ₄ ) ₂ .

JP-A-8-45545 Special table 2002-519352 gazette JP 2000-268863 A

  However, the demand for long-term reliability has increased as the size of lithium ion batteries has increased, and durability performance far exceeding the specifications of various portable electronic device power supplies is eagerly desired. In addition, research and development aimed at improving energy density, such as innovative batteries using metallic lithium anodes, is also active.

  The present invention has been made in view of the above circumstances. Therefore, the present invention suppresses reductive decomposition of a non-aqueous electrolyte solution, exhibits excellent durability performance, and can suppress an increase in internal resistance when stored at a high temperature and a non-aqueous secondary solution. An object is to provide a battery.

  The inventors of the present invention have made extensive studies to solve the above-described problems. As a result, even a non-aqueous electrolyte containing a non-aqueous solvent forms a strong SEI when it contains a specific lithium salt and a specific nitrogen-containing cyclic compound as additives, and has excellent durability performance. The present inventors have found that it is possible to suppress an increase in internal resistance when stored at a high temperature, and have completed the present invention.

｛式（１）中、Ｒ^１は、炭素数１〜４のアルキル基、アリル基、プロパギル基、フェニル基、ベンジル基、ピリジル基、アミノ基、ピロリジルメチル基、トリメチルシリル基、ニトリル基、アセチル基、トリフルオロアセチル基、クロロメチル基、メトキシメチル基、イソシアノメチル基、メチルスルホニル基、フェニルスルホニル基、アジ化スルホニル基、ピリジルスルホニル基、２−（トリメチルシリル）エトキシカルボニロキシ基、ビス（Ｎ，Ｎ’−アルキル）アミノメチル基、又はビス（Ｎ，Ｎ’−アルキル）アミノエチル基であり、Ｒ^２は、炭素数１〜４のアルキル基、炭素数１〜４のフッ素置換アルキル基、炭素数１〜４のアルコキシ基、炭素数１〜４のフッ素置換アルコキシ基、ニトリル基、ニトロ基、アミノ基、又はハロゲン原子であり、そして、ｋは０〜４の整数である。｝で表される化合物と、を含有し、かつ、
シュウ酸リチウムの含有量が０〜５００ｐｐｍであることを特徴とする、非水系電解液。
［２］前記シュウ酸基を有する有機リチウム塩が、ＬｉＢ（Ｃ_２Ｏ_４）_２及びＬｉＢＦ_２（Ｃ_２Ｏ_４）で表されるリチウム塩から選ばれる少なくとも１種のリチウム塩である、前記［１］に記載の非水系電解液。
［３］前記一般式（１）で表される化合物のＲ^１が炭素数１〜４のアルキル基であり、ｋが０である、前記［１］又は［２］に記載の非水系電解液。
［４］前記非水系溶媒が環状カーボネートを含むものである、前記［１］〜［３］のいずれか１項に記載の非水系電解液。
［５］前記非水系溶媒がアセトニトリルを実質的に含まないものである、前記［１］〜［４］のいずれか１項に記載の非水系電解液。
［６］前記一般式（１）で表される化合物の含有量が、非水系電解液１００質量部に対して０．０１〜１０質量部である、前記［１］〜［５］のいずれか１項に記載の非水系電解液。
［７］前記シュウ酸リチウムを、デカンテーション及び濾過から選ばれる少なくとも１種の方法により除去することを特徴とする、前記［１］〜［６］のいずれか１項に記載の非水系電解液の製造方法。
［８］集電体の片面又は両面に、Ｎｉ、Ｍｎ、及びＣｏから選ばれる少なくとも１種の遷移金属元素を含有する正極活物質層を有する正極、
集電体の片面又は両面に負極活物質層を有する負極、並びに、
前記［１］〜［６］のいずれか１項に記載の非水系電解液を具備することを特徴とする、非水系二次電池。 That is, the present invention is as follows.
[1] a non-aqueous solvent;
An organic lithium salt having an oxalic acid group;
The following general formula (1):

{In Formula (1), R ¹ is an alkyl group having 1 to 4 carbon atoms, allyl group, propargyl group, phenyl group, benzyl group, pyridyl group, amino group, pyrrolidylmethyl group, trimethylsilyl group, nitrile group, acetyl group Group, trifluoroacetyl group, chloromethyl group, methoxymethyl group, isocyanomethyl group, methylsulfonyl group, phenylsulfonyl group, sulfonyl azide group, pyridylsulfonyl group, 2- (trimethylsilyl) ethoxycarbonyloxy group, bis ( N, N′-alkyl) aminomethyl group or bis (N, N′-alkyl) aminoethyl group, and R ² represents an alkyl group having 1 to 4 carbon atoms and a fluorine-substituted alkyl group having 1 to 4 carbon atoms. , An alkoxy group having 1 to 4 carbon atoms, a fluorine-substituted alkoxy group having 1 to 4 carbon atoms, a nitrile group, a nitro group, an amino group, or a halogen Is an atom, and k is an integer of 0-4. And a compound represented by:
A nonaqueous electrolytic solution, wherein the content of lithium oxalate is 0 to 500 ppm.
[2] The organic lithium salt having an oxalic acid group is at least one lithium salt selected from lithium salts represented by LiB (C ₂ O ₄ ) ₂ and LiBF ₂ (C ₂ O ₄ ), The non-aqueous electrolyte solution according to [1].
[3] The nonaqueous electrolytic solution according to [1] or [2], wherein R ^{1 of the} compound represented by the general formula (1) is an alkyl group having 1 to 4 carbon atoms and k is 0. .
[4] The nonaqueous electrolytic solution according to any one of [1] to [3], wherein the nonaqueous solvent includes a cyclic carbonate.
[5] The nonaqueous electrolytic solution according to any one of [1] to [4], wherein the nonaqueous solvent substantially does not contain acetonitrile.
[6] Any of the above [1] to [5], wherein the content of the compound represented by the general formula (1) is 0.01 to 10 parts by mass with respect to 100 parts by mass of the nonaqueous electrolytic solution. The non-aqueous electrolyte solution according to item 1.
[7] The non-aqueous electrolyte according to any one of [1] to [6], wherein the lithium oxalate is removed by at least one method selected from decantation and filtration. Manufacturing method.
[8] A positive electrode having a positive electrode active material layer containing at least one transition metal element selected from Ni, Mn, and Co on one side or both sides of a current collector,
A negative electrode having a negative electrode active material layer on one or both sides of the current collector, and
A non-aqueous secondary battery comprising the non-aqueous electrolyte solution according to any one of [1] to [6].

  According to the present invention, there are provided a non-aqueous electrolyte and a non-aqueous secondary battery that can form a strong SEI, exhibit excellent durability, and suppress an increase in internal resistance when stored at high temperatures. can do.

It is a top view which shows roughly an example of the non-aqueous secondary battery of this embodiment. It is the sectional view on the AA line of the non-aqueous secondary battery of FIG.

  Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. In the present specification, numerical ranges described using “to” include numerical values described before and after.

<1. Overall configuration of non-aqueous secondary battery>
The electrolyte solution of this embodiment can be used for a non-aqueous secondary battery, for example. As the non-aqueous secondary battery of this embodiment, for example,
A positive electrode containing a positive electrode material capable of inserting and extracting lithium ions as a positive electrode active material;
As a negative electrode active material, a negative electrode material capable of inserting and extracting lithium ions, and a negative electrode containing one or more negative electrode materials selected from the group consisting of metallic lithium,
A lithium ion secondary battery comprising

  Specifically, the non-aqueous secondary battery of the present embodiment may be the non-aqueous secondary battery illustrated in FIGS. 1 and 2. Here, FIG. 1 is a plan view schematically showing a non-aqueous secondary battery, and FIG. 2 is a cross-sectional view taken along line AA of FIG.

  The non-aqueous secondary battery 100 includes a laminated electrode body formed by laminating a positive electrode 150 and a negative electrode 160 with a separator 170 in a space 120 of a battery exterior 110 constituted by two aluminum laminate films, and a non-aqueous battery. An electrolytic solution (not shown) is accommodated. The battery exterior 110 is sealed by heat-sealing upper and lower aluminum laminate films at the outer periphery thereof. The laminate in which the positive electrode 150, the separator 170, and the negative electrode 160 are sequentially laminated is impregnated with a non-aqueous electrolyte solution. In FIG. 2, each layer constituting the battery exterior 110 and each layer of the positive electrode 150 and the negative electrode 160 are not shown separately in order to avoid the drawing from being complicated.

  It is preferable that the aluminum laminated film which comprises the battery exterior 110 is what coat | covered both surfaces of aluminum foil with polyolefin resin.

  The positive electrode 150 is connected to the positive electrode lead body 130 in the battery 100. Although not shown, the negative electrode 160 is also connected to the negative electrode lead body 140 in the battery 1. Each of the positive electrode lead body 130 and the negative electrode lead body 140 is drawn to the outside of the battery outer casing 110 so that it can be connected to an external device or the like. It is heat-sealed with the sides.

  In the non-aqueous secondary battery 100 illustrated in FIGS. 1 and 2, the positive electrode 150 and the negative electrode 160 each have a single laminated electrode body. It can be increased as appropriate. In the case of a laminated electrode body having a plurality of each of the positive electrode 150 and the negative electrode 160, the tabs of the same electrode may be joined by welding or the like, and then joined to one lead body by welding or the like and taken out of the battery. As the tab of the same polarity, an aspect constituted by an exposed portion of the current collector, an aspect constituted by welding a metal piece to the exposed portion of the current collector, and the like are possible.

  The positive electrode 150 includes a positive electrode active material layer made from a positive electrode mixture and a positive electrode current collector. The negative electrode 160 includes a negative electrode active material layer made from a negative electrode mixture and a negative electrode current collector. The positive electrode 150 and the negative electrode 160 are disposed so that the positive electrode active material layer and the negative electrode active material layer face each other with the separator 170 interposed therebetween.

  Hereinafter, the term “electrode” is abbreviated as a generic term for the positive electrode and the negative electrode, the term “electrode active material layer” is a generic term for the positive electrode active material layer and the negative electrode active material layer, and the term “electrode mixture” is generically termed for the positive electrode mixture and the negative electrode mixture.

  As each of these members, a material provided in a conventional lithium ion secondary battery can be used as long as each requirement in the present embodiment is satisfied. For example, the following materials may be used. Hereinafter, each member of the non-aqueous secondary battery will be described in detail.

｛式（１）中、Ｒ^１は、炭素数１〜４のアルキル基、アリル基、プロパギル基、フェニル基、ベンジル基、ピリジル基、アミノ基、ピロリジルメチル基、トリメチルシリル基、ニトリル基、アセチル基、トリフルオロアセチル基、クロロメチル基、メトキシメチル基、イソシアノメチル基、メチルスルホニル基、フェニルスルホニル基、アジ化スルホニル基、ピリジルスルホニル基、２−（トリメチルシリル）エトキシカルボニロキシ基、ビス（Ｎ，Ｎ’−アルキル）アミノメチル基、又はビス（Ｎ，Ｎ’−アルキル）アミノエチル基であり、Ｒ^２は、炭素数１〜４のアルキル基、炭素数１〜４のフッ素置換アルキル基、炭素数１〜４のアルコキシ基、炭素数１〜４のフッ素置換アルコキシ基、ニトリル基、ニトロ基、アミノ基、又はハロゲン原子であり、そして、ｋは０〜４の整数である。｝で表される化合物と、を含有し、かつ、
シュウ酸リチウムの含有量が０〜５００ｐｐｍである。 <2. Electrolyte>
The non-aqueous electrolyte solution of the present embodiment (hereinafter also simply referred to as “electrolyte solution”)
A non-aqueous solvent,
An organic lithium salt having an oxalic acid group;
The following general formula (1):

{In Formula (1), R ¹ is an alkyl group having 1 to 4 carbon atoms, allyl group, propargyl group, phenyl group, benzyl group, pyridyl group, amino group, pyrrolidylmethyl group, trimethylsilyl group, nitrile group, acetyl group Group, trifluoroacetyl group, chloromethyl group, methoxymethyl group, isocyanomethyl group, methylsulfonyl group, phenylsulfonyl group, sulfonyl azide group, pyridylsulfonyl group, 2- (trimethylsilyl) ethoxycarbonyloxy group, bis ( N, N′-alkyl) aminomethyl group or bis (N, N′-alkyl) aminoethyl group, and R ² represents an alkyl group having 1 to 4 carbon atoms and a fluorine-substituted alkyl group having 1 to 4 carbon atoms. , An alkoxy group having 1 to 4 carbon atoms, a fluorine-substituted alkoxy group having 1 to 4 carbon atoms, a nitrile group, a nitro group, an amino group, or a halogen Is an atom, and k is an integer of 0-4. And a compound represented by:
The content of lithium oxalate is 0 to 500 ppm.

  It is preferable that the non-aqueous electrolyte solution of the present embodiment does not substantially contain moisture. In the present specification, “substantially does not contain” means that a very small amount of the target component may be contained as long as it does not inhibit the solution of the problem of the present invention. The water content is preferably 0 to 100 ppm with respect to the total amount of the electrolytic solution.

  The non-aqueous electrolyte solution of the present embodiment preferably does not substantially contain acetonitrile, and more preferably does not contain acetonitrile. The non-aqueous electrolyte solution is preferable from the viewpoint of suppressing negative electrode deterioration when it does not substantially contain acetonitrile.

<2-1. Non-aqueous solvent>
The “non-aqueous solvent” in the present embodiment refers to an element obtained by removing a lithium salt and a nitrogen-containing cyclic compound from an electrolyte solution. The lithium salt and nitrogen-containing cyclic compound described later are not included in the non-aqueous solvent.

  Examples of the non-aqueous solvent include alcohols such as methanol and ethanol; aprotic solvents and the like. Among these, an aprotic polar solvent is preferable.

Among the non-aqueous solvents, specific examples of the aprotic solvent include, for example, ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, trans-2,3-butylene carbonate, cis-2,3-butylene carbonate, 1,2-pentylene carbonate, trans-2,3-pentylene carbonate, cis-2,3-pentylene carbonate, and cyclic carbonates typified by vinylene carbonate, 4,5-dimethylvinylene carbonate, and vinylethylene carbonate 4-fluoro-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, cis-4,5-difluoro-1,3-dioxolan-2-one, trans -4,5-difluoro-1,3-dioxolan-2-o 4,4,5-trifluoro-1,3-dioxolan-2-one, 4,4,5,5-tetrafluoro-1,3-dioxolan-2-one, and 4,4,5-trifluoro Fluoroethylene carbonate typified by -5-methyl-1,3-dioxolan-2-one; typified by γ-butyrolactone, γ-valerolactone, γ-caprolactone, δ-valerolactone, δ-caprolactone, and ε-caprolactone Lactones; ethylene sulfite, propylene sulfite, butylene sulfite, pentene sulfite, sulfolane, 3-methylsulfolane, 1,3-propane sultone, 1,4-butane sultone, 1-propene 1,3-sultone, dimethyl Sulfoxide, tetramethylene sulfoxide, and ethylene glycol sulfide Sulfur compounds represented by: cyclic ethers represented by tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, and 1,3-dioxane; ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate , Chain carbonates typified by dipropyl carbonate, methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, and methyl trifluoroethyl carbonate; typified by trifluorodimethyl carbonate, trifluorodiethyl carbonate, and trifluoroethyl methyl carbonate Chain fluorinated carbonate: acetonitrile, propionitrile, butyronitrile, valeronitrile, benzonitrile And mononitriles represented by acrylonitrile; alkoxy group-substituted nitriles represented by methoxyacetonitrile and 3-methoxypropionitrile; malononitrile, succinonitrile, glutaronitrile, adiponitrile, 1,4-dicyanoheptane, 1, 5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 2,6-dicyanoheptane, 1,8-dicyanooctane, 2,7-dicyanooctane, 1,9-dicyanononane, 2,8- Dicyanononane, 1,10-dicyanodecane, 1,6-dicyanodecane, and dinitriles represented by 2,4-dimethylglutaronitrile; cyclic nitriles represented by benzonitrile; chain esters represented by methyl propionate Dimethoxyethane, diethyl ether , 1,3-dioxolane, diglyme, triglyme, and a chain ether represented by ^tetraglyme; Rf ^{4 -OR} 5 (Rf 4 is an alkyl group containing fluorine atom, ^{R 5} may contain a fluorine atom Fluorinated ethers typified by organic groups); ketones typified by acetone, methyl ethyl ketone, and methyl isobutyl ketone, and halides typified by these fluorinated products. These are used singly or in combination of two or more.

  Among these other non-aqueous solvents, it is more preferable to use one or more of cyclic carbonates and chain carbonates. Here, only one of those exemplified above as the cyclic carbonate and the chain carbonate may be selected and used, or two or more (for example, two or more of the above-mentioned cyclic carbonates, the above examples) Two or more of the chain carbonates, or one or more of the exemplified cyclic carbonates and two or more of the exemplified chain carbonates may be used. Among these, ethylene carbonate, propylene carbonate, vinylene carbonate, or fluoroethylene carbonate is more preferable as the cyclic carbonate, and ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate is more preferable as the chain carbonate. It is more preferable to use a cyclic carbonate.

  Although there is no restriction | limiting in particular about content of a cyclic carbonate, It is preferable that it is 3-100 volume% with respect to the whole quantity of a non-aqueous solvent. From the viewpoint of dissociating ions, the content of the cyclic carbonate is more preferably 5% by volume or more, and further preferably 10% by volume or more with respect to the total amount of the non-aqueous solvent. Further, from the viewpoint of lowering the viscosity, it is more preferably 85% by volume or less, and further preferably 66% by volume or less. When content of cyclic carbonate is 10 volume% or more with respect to the whole quantity of a non-aqueous solvent, melt | dissolution of lithium salt can be accelerated | stimulated. When the content of the cyclic carbonate in the non-aqueous solvent is within the above range, the high temperature durability performance and other battery characteristics tend to be further improved while maintaining the excellent performance of the cyclic carbonate. is there.

<2-2. Lithium salt>
In this embodiment, the lithium salt includes an organic lithium salt having an oxalic acid group. Addition of an organic lithium salt having an oxalic acid group is effective in improving load characteristics and charge / discharge cycle characteristics of a non-aqueous secondary battery.

  Here, “organic lithium salt” refers to a lithium salt containing a carbon atom as an anion, and “inorganic lithium salt” refers to a lithium salt not containing a carbon atom as an anion. The “fluorine-containing inorganic lithium salt” refers to a lithium salt that does not contain a carbon atom in an anion and contains a fluorine atom in an anion.

Specific examples of the organic lithium salt having an oxalic acid group include, for example, LiB (C ₂ O ₄ ) ₂ , LiBF ₂ (C ₂ O ₄ ), LiPF ₄ (C ₂ O ₄ ), and LiPF ₂ (C ₂ O ₄ ) An organic lithium salt represented by each of _{2 and} the like, and among others, at least one lithium salt selected from lithium salts represented by LiB (C ₂ O ₄ ) ₂ and LiBF ₂ (C ₂ O ₄ ) Is preferred. Moreover, it is more preferable to use 1 type, or 2 or more types of these with fluorine-containing inorganic lithium salt.

  The addition amount of the organolithium salt having an oxalic acid group to the non-aqueous electrolyte is, as the amount per 1 L of the non-aqueous solvent, of the non-aqueous electrolyte is 0. The amount is preferably 005 mol or more, more preferably 0.02 mol or more, and further preferably 0.05 mol or more. However, if the amount of the organic lithium salt having an oxalic acid group in the non-aqueous electrolyte is too large, it may be precipitated. Therefore, the addition amount of the organic lithium salt having an oxalic acid group to the non-aqueous electrolyte is preferably less than 1.0 mol per liter of the non-aqueous solvent of the non-aqueous electrolyte. More preferably, it is less than 5 mol, and still more preferably less than 0.2 mol.

  The organic lithium salt having an oxalic acid group is known to be hardly soluble in an organic solvent having a low polarity, particularly a chain carbonate. The organic lithium salt having an oxalate group may contain a small amount of lithium oxalate, and when mixed as a non-aqueous electrolyte, it reacts with a small amount of water contained in other raw materials. In some cases, a white precipitate of lithium oxalate is newly generated. The inventors have found that the presence of a large amount of this lithium oxalate can be a major obstacle as an electrochemical resistance component in a non-aqueous secondary battery. Therefore, the content of lithium oxalate in the nonaqueous electrolytic solution of the present embodiment is 0 to 500 ppm. The content of lithium oxalate is preferably 0 to 300 ppm, and more preferably 0 to 50 ppm. Moreover, it is preferable to remove by at least one method selected from decantation and filtration so that the content of lithium oxalate is within the above range.

In the present embodiment, the fluorine-containing inorganic lithium salt is excellent in that it forms a passive film on the surface of the metal foil that is the positive electrode current collector and suppresses corrosion of the positive electrode current collector. It is also excellent from the viewpoint of solubility, conductivity, and ionization degree. Specific examples of the fluorine-containing inorganic lithium salt include, for example, LiPF ₆ , LiBF ₄ , LiAsF ₆ , Li ₂ SiF ₆ , LiSbF ₆ , Li ₂ B ₁₂ F _b H _12-b [b is an integer of 0 to 3], LiN _(SO 2 _{F) 2} and the like.

These fluorine-containing inorganic lithium salts are used singly or in combination of two or more. As the fluorine-containing inorganic lithium salt, a compound that is a double salt of LiF and a Lewis acid is desirable. Among them, the use of a fluorine-containing inorganic lithium salt having a phosphorus atom is more preferable because it easily releases a free fluorine atom, LiPF ₆ is particularly preferred. Further, when a fluorine-containing inorganic lithium salt having a boron atom is used as the fluorine-containing inorganic lithium salt, it is preferable because an excessive free acid component that may cause battery deterioration is easily captured. From such a viewpoint, LiBF ₄ is particularly preferred.

  Although there is no restriction | limiting in particular about content of the fluorine-containing inorganic lithium salt in the non-aqueous electrolyte solution of this embodiment, It is preferable that it is 0.2 mol or more with respect to 1 L of non-aqueous solvents, and it is 0.5 mol or more. Is more preferable, and it is still more preferable that it is 0.8 mol or more. Moreover, it is preferable that it is 15 mol or less with respect to 1 L of non-aqueous solvents, It is more preferable that it is 4 mol or less, It is still more preferable that it is 2.8 mol or less. When the content of the fluorine-containing inorganic lithium salt is within the above range, the ionic conductivity tends to increase and high output characteristics tend to be exhibited.

In addition to the fluorine-containing inorganic lithium salt, a lithium salt generally used for a non-aqueous secondary battery may be supplementarily added as the lithium salt in the present embodiment. Specific examples of other lithium salts include inorganic lithium salts that do not contain fluorine atoms such as LiClO ₄ , LiAlO ₄ , LiAlCl ₄ , LiB ₁₀ Cl ₁₀ , and chloroborane Li in the anion; LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , Li ₂ C ₂ F ₄ (SO ₃ ) ₂ , LiC (CF ₃ SO ₂ ) ₃ , LiC _n F _{2n + 1} SO ₃ (n ≧ 2), lower aliphatic carboxylic acid Li, tetraphenylborate Li, etc. An organic lithium salt represented by LiN (SO ₂ C _m F _{2m + 1} ) ₂ [m is an integer of 1 to 8] such as LiN (SO ₂ CF ₃ ) ₂ or LiN (SO ₂ C ₂ F ₅ ) ₂ ; ₅ (CF ₃ ) and the like LiPF _n (C _p F _{2p + 1} ) _6-n [n is an integer of 1 to 5, p is an integer of 1 to 8] Salt; LiBF _q (C _s F _{2s + 1} ) _4-q such as LiBF ₃ (CF ₃ ) _4-q [q is an integer of 1 to 3, s is an integer of 1 to 8]; A bonded lithium salt; the following general formulas (2a), (2b), and (2c);
^{_{LiC (SO 2 R 6) (}} SO 2 R 7) (SO 2 R 8) (2a)
LiN (SO ₂ OR ⁹ ) (SO ₂ OR ¹⁰ ) (2b)
LiN (SO ₂ R ¹¹ ) (SO ₂ OR ¹² ) (2c)
{Wherein R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , R ¹¹ , and R ¹² may be the same as or different from each other, and represent a C 1-8 perfluoroalkyl group. Show. }, And one or more of them can be used together with an organic lithium salt having an oxalic acid group.

｛式（１）中、Ｒ^１は、炭素数１〜４のアルキル基、アリル基、プロパギル基、フェニル基、ベンジル基、ピリジル基、アミノ基、ピロリジルメチル基、トリメチルシリル基、ニトリル基、アセチル基、トリフルオロアセチル基、クロロメチル基、メトキシメチル基、イソシアノメチル基、メチルスルホニル基、フェニルスルホニル基、アジ化スルホニル基、ピリジルスルホニル基、２−（トリメチルシリル）エトキシカルボニロキシ基、ビス（Ｎ，Ｎ’−アルキル）アミノメチル基、又はビス（Ｎ，Ｎ’−アルキル）アミノエチル基であり、Ｒ^２は、炭素数１〜４のアルキル基、炭素数１〜４のフッ素置換アルキル基、炭素数１〜４のアルコキシ基、炭素数１〜４のフッ素置換アルコキシ基、ニトリル基、ニトロ基、アミノ基、又はハロゲン原子であり、そして、ｋは０〜４の整数である。｝で表される窒素含有環状化合物を含有することを特徴としている。 <2-3. Nitrogen-containing cyclic compound>
The electrolytic solution in the present embodiment has the following general formula (1) as an additive:

{In Formula (1), R ¹ is an alkyl group having 1 to 4 carbon atoms, allyl group, propargyl group, phenyl group, benzyl group, pyridyl group, amino group, pyrrolidylmethyl group, trimethylsilyl group, nitrile group, acetyl group Group, trifluoroacetyl group, chloromethyl group, methoxymethyl group, isocyanomethyl group, methylsulfonyl group, phenylsulfonyl group, sulfonyl azide group, pyridylsulfonyl group, 2- (trimethylsilyl) ethoxycarbonyloxy group, bis ( N, N′-alkyl) aminomethyl group or bis (N, N′-alkyl) aminoethyl group, and R ² represents an alkyl group having 1 to 4 carbon atoms and a fluorine-substituted alkyl group having 1 to 4 carbon atoms. , An alkoxy group having 1 to 4 carbon atoms, a fluorine-substituted alkoxy group having 1 to 4 carbon atoms, a nitrile group, a nitro group, an amino group, or a halogen Is an atom, and k is an integer of 0-4. } It contains the nitrogen-containing cyclic compound represented by this.

Specific examples of the nitrogen-containing cyclic compound in the present embodiment are exemplified below. These are used singly or in combination of two or more.

Here, since the number of moles per unit mass increases as the molecular weight decreases, R ¹ of the compound represented by the general formula (1) is preferably an alkyl group having 1 to 4 carbon atoms, and k is 0. Preferably there is. By using both an organic lithium salt having an oxalic acid group and a nitrogen-containing cyclic compound, a strong SEI is formed, which exhibits excellent durability and suppresses an increase in internal resistance when stored at high temperatures. be able to.

  Although there is no restriction | limiting in particular about content of the nitrogen-containing cyclic compound in the electrolyte solution in this embodiment, It is preferable that it is 0.01-10 mass% on the basis of the whole quantity of electrolyte solution, and 0.02-5 It is more preferable that it is mass%, and it is still more preferable that it is 0.03-3 mass%. In this embodiment, the nitrogen-containing cyclic compound forms a strong SEI when used with an organolithium salt having an oxalic acid group. Therefore, the non-aqueous secondary battery containing both the organic lithium salt having an oxalic acid group and the nitrogen-containing cyclic compound exhibits excellent durability and suppresses an increase in internal resistance when stored at high temperatures. it can. However, the nitrogen-containing cyclic compound in the present embodiment is not necessarily highly soluble due to the influence of the π conjugate plane. Therefore, by adjusting the content of the nitrogen-containing cyclic compound within the above-mentioned range, it is possible to form a strong SEI without impairing the basic function as a non-aqueous secondary battery. The increase in resistance can be reduced. By preparing the electrolytic solution with such a composition, all of the battery characteristics tend to be further improved in the obtained non-aqueous secondary battery.

<2-4. Other optional additives>
In the present embodiment, for the purpose of improving the charge / discharge cycle characteristics of the non-aqueous secondary battery, high-temperature storage property, improving safety (for example, preventing overcharge, etc.), the non-aqueous electrolyte solution includes, for example, anhydrous acid, Sulfonic acid ester, diphenyl disulfide, cyclohexylbenzene, biphenyl, fluorobenzene, tert-butylbenzene, phosphoric acid ester [ethyl diethylphosphonoacetate (EDPA): (C ₂ H ₅ O) ₂ (P═O) —CH ₂ ( C═O) OC ₂ H ₅ , tris (trifluoroethyl) phosphate (TFEP): (CF ₃ CH ₂ O) ₃ P═O, triphenyl phosphate (TPP): (C ₆ H ₅ O) ₃ P ═O etc.] and the like, and optional additives selected from derivatives of these compounds and the like can be appropriately contained. In particular, the phosphoric acid ester has an effect of suppressing side reactions during storage and is effective.

<3. Positive electrode>
The positive electrode 150 includes a positive electrode active material layer made from a positive electrode mixture and a positive electrode current collector. The positive electrode 150 is not particularly limited as long as it functions as a positive electrode of a non-aqueous secondary battery, and may be a known one.

  The positive electrode active material layer contains a positive electrode active material and optionally further contains a conductive additive and a binder.

  The positive electrode active material layer preferably contains a material capable of inserting and extracting lithium ions as the positive electrode active material. It is preferable that a positive electrode active material layer contains a conductive support agent and a binder as needed with a positive electrode active material. The use of such a material is preferable because a high voltage and a high energy density tend to be obtained.

Examples of the positive electrode active material include the following general formulas (3a) and (3b):
Li _x MO ₂ (3a)
Li _y M ₂ O ₄ (3b)
{In the formula, M represents one or more metal elements including at least one transition metal element, x represents a number of 0 to 1.1, and y represents a number of 0 to 2. }, A lithium-containing compound represented by each of the above and other lithium-containing compounds.

Examples of the lithium-containing compound represented by each of the general formulas (3a) and (3b) include lithium cobalt oxides typified by LiCoO ₂ ; LiMnO ₂ , LiMn ₂ O ₄ , and Li ₂ Mn ₂ O ₄ . Lithium manganese oxide typified; Lithium nickel oxide typified by LiNiO ₂ ; Li _z MO ₂ (M contains at least one transition metal element selected from Ni, Mn, and Co, and Ni, Mn 2 or more metal elements selected from the group consisting of Co, Al, and Mg, and z represents a number of more than 0.9 and less than 1.2. It is done.

The lithium-containing compound other than the lithium-containing compound represented by each of the general formulas (3a) and (3b) is not particularly limited as long as it contains lithium. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, a metal chalcogenide containing lithium, a metal phosphate compound containing lithium and a transition metal element, and lithium and a transition metal element. (For example, Li _t M _u SiO ₄ , M is as defined in the general formula (3a), t is a number from 0 to 1, and u is a number from 0 to 2). From the viewpoint of obtaining a higher voltage, as the lithium-containing compound, in particular,
With lithium,
Selected from the group consisting of cobalt (Co), nickel (Ni), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), chromium (Cr), vanadium (V), and titanium (Ti) At least one transition metal element,
The composite oxide containing and a metal phosphate compound are preferable.

More specifically, the lithium-containing compound is more preferably a composite oxide containing lithium and a transition metal element or a metal chalcogenide containing lithium and a transition metal element, and a metal phosphate compound containing lithium. General formulas (4a) and (4b):
^{_{Li v M I D 2 (4a}} )
Li _w M ^II PO ₄ (4b)
{Wherein D represents oxygen or a chalcogen element, M ^I and M ^II each represent one or more transition metal elements, and the values of v and w depend on the charge / discharge state of the battery, and v is 0.05 -1.10, w shows the number of 0.05-1.10. }, Compounds represented by each of the above.

  The lithium-containing compound represented by the above general formula (4a) has a layered structure, and the compound represented by the above general formula (4b) has an olivine structure. These lithium-containing compounds are obtained by substituting a part of the transition metal element with Al, Mg, or other transition metal elements for the purpose of stabilizing the structure, and include these metal elements in the grain boundaries. It is also possible that the oxygen atom is partially substituted with a fluorine atom or the like, or at least a part of the surface of the positive electrode active material is coated with another positive electrode active material.

  As the positive electrode active material in the present embodiment, only the lithium-containing compound as described above may be used, or other positive electrode active material may be used in combination with the lithium-containing compound.

Examples of such other positive electrode active materials include metal oxides or metal chalcogenides having a tunnel structure and a layered structure; sulfur; a conductive polymer. Examples of the metal oxide or metal chalcogenide having a tunnel structure and a layered structure include MnO ₂ , FeO ₂ , FeS ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , TiS ₂ , MoS ₂ , and NbSe. ₂ includes oxides, sulfides, selenides, and the like of metals other than lithium. Examples of the conductive polymer include conductive polymers represented by polyaniline, polythiophene, polyacetylene, and polypyrrole.

  The other positive electrode active materials described above are used alone or in combination of two or more, and are not particularly limited. However, since it is possible to occlude and release lithium ions in a reversible manner and to achieve a high energy density, the positive electrode active material layer is at least one transition metal selected from Ni, Mn, and Co. It is preferable to contain an element.

  When a lithium-containing compound and another positive electrode active material are used in combination as the positive electrode active material, the use ratio of both is preferably 80% by mass or more, and 85% by mass as the use ratio of the lithium-containing compound to the entire positive electrode active material. % Or more is more preferable.

  Examples of the conductive aid include carbon black typified by graphite, acetylene black, and ketjen black, and carbon fiber. The content ratio of the conductive assistant is preferably 10 parts by mass or less, more preferably 1 to 5 parts by mass with respect to 100 parts by mass of the positive electrode active material.

  Examples of the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid, styrene butadiene rubber, and fluorine rubber. The content ratio of the binder is preferably 6 parts by mass or less, more preferably 0.5 to 4 parts by mass with respect to 100 parts by mass of the positive electrode active material.

  The positive electrode active material layer is formed by applying a positive electrode mixture-containing slurry, in which a positive electrode mixture obtained by mixing a positive electrode active material and, if necessary, a conductive additive and a binder in a solvent, is applied to a positive electrode current collector and dried (solvent removal) And is formed by pressing as necessary. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used. For example, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, water and the like can be mentioned.

  The positive electrode current collector is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode current collector may have a surface coated with a carbon coat or may be processed into a mesh shape. The thickness of the positive electrode current collector is preferably 5 to 40 μm, more preferably 7 to 35 μm, and still more preferably 9 to 30 μm.

<4. Negative electrode>
The negative electrode 160 includes a negative electrode active material layer made from a negative electrode mixture and a negative electrode current collector. The negative electrode 160 is not particularly limited as long as it functions as a negative electrode of a non-aqueous secondary battery, and may be a known one.

From the viewpoint that the negative electrode active material layer can increase the battery voltage, lithium ion as a negative electrode active material is 0.4 V vs. It is preferable to contain a material that can be occluded at a lower potential than Li / Li ⁺ . It is preferable that a negative electrode active material layer contains a conductive support agent and a binder as needed with a negative electrode active material.

  Examples of the negative electrode active material include amorphous carbon (hard carbon), artificial graphite, natural graphite, graphite, pyrolytic carbon, coke, glassy carbon, organic polymer compound fired body, mesocarbon microbeads, carbon fiber, activated carbon In addition to carbon materials such as graphite, carbon colloid, and carbon black, metal lithium, metal oxide, metal nitride, lithium alloy, tin alloy, silicon alloy, intermetallic compound, organic compound, inorganic compound, metal complex And organic polymer compounds.

  A negative electrode active material is used individually by 1 type or in combination of 2 or more types.

  Examples of the conductive aid include carbon black typified by graphite, acetylene black, and ketjen black, and carbon fiber. The content ratio of the conductive assistant is preferably 20 parts by mass or less, more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the negative electrode active material.

  Examples of the binder include PVDF, PTFE, polyacrylic acid, styrene butadiene rubber, and fluorine rubber. The content ratio of the binder is preferably 10 parts by mass or less, more preferably 0.5 to 6 parts by mass with respect to 100 parts by mass of the negative electrode active material.

  The negative electrode active material layer is coated with a negative electrode mixture-containing slurry in which a negative electrode mixture obtained by mixing a negative electrode active material and, if necessary, a conductive additive and a binder is dispersed in a solvent, and dried (solvent removal). And it forms by pressing as needed. There is no restriction | limiting in particular as such a solvent, A conventionally well-known thing can be used. For example, N-methyl-2-pyrrolidone, dimethylformamide, dimethylacetamide, water and the like can be mentioned.

  The negative electrode current collector is made of a metal foil such as a copper foil, a nickel foil, or a stainless steel foil. The negative electrode current collector may have a carbon coating on the surface or may be processed into a mesh shape. The thickness of the negative electrode current collector is preferably 5 to 40 μm, more preferably 6 to 35 μm, and still more preferably 7 to 30 μm.

<5. Separator>
The nonaqueous secondary battery 100 in the present embodiment preferably includes a separator 170 between the positive electrode 150 and the negative electrode 160 from the viewpoint of providing safety such as prevention of short circuit between the positive electrode 150 and the negative electrode 160 and shutdown. The separator 170 may be the same as that provided in a known non-aqueous secondary battery, and is preferably an insulating thin film having high ion permeability and excellent mechanical strength. Examples of the separator 170 include a woven fabric, a nonwoven fabric, and a synthetic resin microporous membrane. Among these, a synthetic resin microporous membrane is preferable.

  As the synthetic resin microporous membrane, for example, a microporous membrane containing polyethylene or polypropylene as a main component or a polyolefin microporous membrane such as a microporous membrane containing both of these polyolefins is suitably used. Examples of the nonwoven fabric include a porous film made of a heat resistant resin such as glass, ceramic, polyolefin, polyester, polyamide, liquid crystal polyester, and aramid.

  The separator 170 may have a configuration in which one type of microporous membrane is laminated or a plurality of microporous membranes may be laminated, or two or more types of microporous membranes may be laminated. The separator 170 may have a configuration in which a single layer or a plurality of layers are stacked using a mixed resin material obtained by melting and kneading two or more kinds of resin materials.

<6. Battery exterior>
Although the structure of the battery exterior 110 of the non-aqueous secondary battery 100 in this embodiment is not specifically limited, For example, any battery exterior of a battery can and a laminate film exterior body can be used. As the battery can, for example, a metal can made of steel or aluminum can be used. As the laminate film outer package, for example, a laminate film having a three-layer structure of hot melt resin / metal film / resin can be used.

  Laminate film exterior is in a state where two sheets are stacked with the hot-melt resin side facing inward, or folded so that the hot-melt resin side faces inward, and the end is sealed by heat sealing It can be used as an exterior body. When using a laminate film exterior body, the positive electrode lead body 130 (or a lead tab connected to the positive electrode terminal and the positive electrode terminal) is connected to the positive electrode current collector, and the negative electrode lead body 140 (or the negative electrode terminal and the negative electrode terminal) is connected to the negative electrode current collector. A lead tab to be connected) may be connected. In this case, the laminate film exterior body is sealed with the ends of the positive electrode lead body 130 and the negative electrode lead body 140 (or the lead tab connected to each of the positive electrode terminal and the negative electrode terminal) pulled out of the exterior body. Also good.

<7. Method for producing non-aqueous electrolyte>
The non-aqueous electrolyte solution of the present embodiment includes a non-aqueous solvent, an organic lithium salt having an oxalic acid group, a compound represented by the above general formula (1), a fluorine-containing inorganic lithium salt, and a It can manufacture by mixing with the lithium salt currently used for the water-system secondary battery by arbitrary means, and adjusting so that content of lithium oxalate may be 0-500 ppm.

  The mixing procedure is not limited. For example, a non-aqueous solvent is prepared, an organic lithium salt having an oxalic acid group with respect to the mixed solvent, and a fluorine-containing inorganic lithium salt or a lithium salt generally used for non-aqueous secondary batteries as necessary. In addition, a non-aqueous electrolyte can be obtained by adding and mixing the compound represented by the general formula (1) described above.

  The method for adjusting the content of lithium oxalate to be 0 to 500 ppm is not particularly limited. For example, a non-aqueous electrolyte is manufactured using an organic lithium salt with a low content of lithium oxalate in advance, and as a result, the content of lithium oxalate contained in the non-aqueous electrolyte is 0 to 500 ppm. Good.

  Moreover, it is preferable to remove lithium oxalate by at least one method selected from decantation and filtration. For example, after preparing the non-aqueous electrolyte, it is preferable to adjust by removing lithium oxalate from the non-aqueous electrolyte by at least one method selected from decantation and filtration.

<8. Battery Manufacturing Method>
The non-aqueous secondary battery 100 in this embodiment has the above-described non-aqueous electrolyte solution, the positive electrode 150 having a positive electrode active material layer on one or both sides of the current collector, and the negative electrode active material layer on one or both sides of the current collector. It is produced by a known method using the negative electrode 160, the battery outer casing 110, and, if necessary, the separator 170.

First, the laminated body which consists of the positive electrode 150 and the positive electrode 160 and the separator 170 as needed is formed. For example, a mode in which a long positive electrode 150 and a negative electrode 160 are wound in a stacked state in which the long separator is interposed between the positive electrode 150 and the negative electrode 160 to form a stacked body having a wound structure;
A mode of forming a laminate having a laminated structure in which a positive electrode sheet and a negative electrode sheet obtained by cutting the positive electrode 150 and the negative electrode 160 into a plurality of sheets having a certain area and shape are alternately laminated via a separator sheet. ;
A mode of forming a laminated body having a laminated structure in which long separators are folded in a zigzag manner, and positive electrode sheets and negative electrode sheets are alternately inserted between the zipped separators;
Etc. are possible.

  Next, the above-described laminated body is accommodated in the battery exterior 110 (battery case), the electrolytic solution according to this embodiment is injected into the battery case, and the laminated body is immersed in the electrolytic solution and sealed. The nonaqueous secondary battery in this embodiment can be produced.

  Alternatively, an electrolyte solution in a gel state is prepared in advance by impregnating a base material made of a polymer material with an electrolytic solution, and a sheet-like positive electrode 150, a negative electrode 160, an electrolyte membrane, and, if necessary, a separator 170. A non-aqueous secondary battery 100 can also be produced by forming a laminated body having a laminated structure using the battery and housing the battery in the battery exterior 110.

  The shape of the non-aqueous secondary battery 100 in the present embodiment is not particularly limited, and for example, a cylindrical shape, an elliptical shape, a rectangular tube shape, a button shape, a coin shape, a flat shape, a laminated shape, and the like are suitably employed.

  In addition, as for the arrangement of the electrodes, there is a portion where the outer peripheral end of the negative electrode active material layer and the outer peripheral end of the positive electrode active material layer overlap, or there is a portion where the width is too small in the non-opposing portion of the negative electrode active material layer. When it is designed in such a manner, there is a possibility that the charge / discharge cycle characteristics in the non-aqueous secondary battery may be deteriorated due to the displacement of the electrode during battery assembly. Therefore, it is preferable that the electrode body used for the non-aqueous secondary battery is previously fixed with a tape such as polyimide tape, polyphenylene sulfide tape, PP tape, an adhesive, or the like.

  The non-aqueous secondary battery 100 in the present embodiment can function as a battery by the initial charge, but is stabilized when a part of the electrolytic solution is decomposed during the initial charge. Although there is no restriction | limiting in particular about the method of initial charge, It is preferable that initial charge is performed at 0.001-0.3C, It is more preferable to be performed at 0.002-0.25C, 0.003-0.2C More preferably, it is performed. It is also preferable that the initial charging is performed via a constant voltage charging in the middle. The constant current for discharging the rated capacity in 1 hour is 1C. By setting a long voltage range in which the lithium salt is involved in the electrochemical reaction, SEI is formed on the surface of the electrode and has an effect of suppressing an increase in internal resistance including the positive electrode 5 as well as a reaction product. Is not firmly fixed only to the negative electrode 6, and in some form, a good effect is given to members other than the negative electrode 6 such as the positive electrode 5 and the separator 7. For this reason, it is very effective to perform the initial charge in consideration of the electrochemical reaction of the lithium salt dissolved in the non-aqueous electrolyte.

  The non-aqueous secondary battery 1 in this embodiment can also be used as a battery pack in which a plurality of non-aqueous secondary batteries 1 are connected in series or in parallel. From the viewpoint of managing the charge / discharge state of the battery pack, the operating voltage range per unit is preferably 2 to 5 V, more preferably 2.5 to 5 V, and 2.75 V to 5 V. Particularly preferred.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the above-mentioned embodiment. The present invention can be variously modified without departing from the gist thereof.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

Various evaluations were performed as follows.
(1) Production of battery (1-1) Production of positive electrode (P1) Composite oxide of lithium, nickel, manganese and cobalt having a number average particle diameter of 11 μm (LiNi _1/3 Mn _1/3 Co _1/3 ) as a positive electrode active material O ₂ , density 4.70 g / cm ³ ), graphite carbon powder having a number average particle diameter of 6.5 μm (density 2.26 g / cm ³ ) and acetylene black powder having a number average particle diameter of 48 nm (density 1) as a conductive assistant. and .95g / cm ^3), polyvinylidene fluoride (PVdF as a binder; and density of ^{1.75g / cm 3), 100:} 4.2: 1.8: were mixed at a mass ratio of 4.6, the positive electrode mixture Got. N-methyl-2-pyrrolidone as a solvent was added to the obtained positive electrode mixture so as to have a solid content of 68% by mass and further mixed to prepare a positive electrode mixture-containing slurry. The positive electrode mixture-containing slurry was applied to one surface of an aluminum foil having a thickness of 20 μm and a width of 200 mm to be a positive electrode current collector by a doctor blade method while adjusting the basis weight to be 23.8 mg / cm ² . The solvent was removed by drying. Then, the positive electrode (P1) which consists of a positive electrode active material layer and a positive electrode electrical power collector was obtained by rolling so that the density of a positive electrode active material layer might be 2.86 g / cm < ³ > with a roll press.

(1-2) Production of negative electrode (N1) Graphite carbon powder having a number average particle diameter of 12.7 μm (density 2.23 g / cm ³ ) and graphite carbon powder having a number average particle diameter of 6.5 μm (density 2) as a negative electrode active material .27 g / cm ³ ), carboxymethyl cellulose (density 1.60 g / cm ³ ) solution (solid content concentration 1.83% by mass) and styrene butadiene latex (glass transition temperature: −5 ° C., number average during drying) as binders Particle diameter: 120 nm, density: 1.00 g / cm ³ , dispersion medium: water, solid content concentration: 40 mass%) mixed at a solid content mass ratio of 87.2: 9.7: 1.4: 1.7 As a result, a negative electrode mixture was obtained. Water was added to the obtained negative electrode mixture as a solvent so as to have a solid content of 45% by mass, and further mixed to prepare a negative electrode mixture-containing slurry. The negative electrode mixture-containing slurry was applied to one side of a copper foil having a thickness of 10 μm and a width of 200 mm to be a negative electrode current collector by a doctor blade method while adjusting the basis weight to be 10.6 mg / cm ^2. Was removed by drying. Then, it rolled so that the density of a negative electrode active material layer might be 1.52 g / cm < ³ > with a roll press, and the negative electrode (N1) which consists of a negative electrode active material layer and a negative electrode collector was obtained.

(1-3) Manufacture of coin-type non-aqueous secondary battery In the center of a CR2032-type battery case (SUS304 / Al clad), the positive electrode obtained as described above was punched into a disk shape with a diameter of 15.958 mm. Was set with the positive electrode active material layer facing upward. In this positive electrode, the area of the positive electrode active material layer was 2.00 cm ² . A glass filter paper (ADVANTEC GA-100) punched out into a disk shape having a diameter of 19 mm and a polypropylene gasket were set, and 150 μL of the electrolyte was injected. Thereafter, the negative electrode obtained as described above was punched into a disk shape having a diameter of 16.156 mm and set with the negative electrode active material layer facing downward. In this negative electrode, the area of the negative electrode active material layer was 2.05 cm ² . Furthermore, after setting one spacer and a spring, the battery cap was fitted and crimped with a caulking machine. The electrolyte that overflowed from the battery case was wiped clean with a waste cloth. The battery case containing the laminate and the non-aqueous electrolyte was held for 24 hours in a 25 ° C. environment, and the laminate was sufficiently impregnated with the electrolyte to obtain a coin-type non-aqueous secondary battery.

(2) Battery Evaluation For the evaluation battery (hereinafter also simply referred to as “battery”) obtained as described above, first, the initial charge process and the initial charge / discharge capacity are performed according to the following procedure (2-1). Measurements were made. Next, each battery was evaluated according to the following procedure (2-2). Charging / discharging was performed using charging / discharging apparatus ACD-01 (trade name) manufactured by Asuka Electronics Co., Ltd. and thermostatic bath PLM-63S (trade name) manufactured by Futaba Kagaku.

  Here, 1C means a current value at which a fully charged battery is discharged at a constant current and is expected to be discharged in 1 hour. In the following, it means a current value that is expected to discharge from a fully charged state of 4.2 V to 3.0 V at a constant current and finish discharging in 1 hour.

(2-1) Initial charge / discharge treatment of coin-type non-aqueous secondary battery The battery temperature is set to 4.2 V by setting the ambient temperature of the battery to 25 ° C. and charging with a constant current of 0.6 mA corresponding to 0.1 C. Then, the battery was charged at a constant voltage of 4.2 V for a total of 15 hours. Thereafter, the battery was discharged to 3.0 V with a constant current of 1.8 mA corresponding to 0.3 C. The initial efficiency was calculated by dividing the discharge capacity at this time by the charge capacity. The discharge capacity at this time was defined as the initial capacity.

(2-2) 85 ° C. full charge storage test of coin-type non-aqueous secondary battery A battery that was first charged and discharged by the method described in (2-1) above was stored in a fully charged state at 85 ° C. The durability performance of the case was evaluated. First, the ambient temperature of the battery was set to 25 ° C., the battery was charged with a constant current of 6 mA corresponding to 1 C, and the battery voltage reached 4.2 V, and then charged with a constant voltage of 4.2 V for a total of 3 hours. . Next, this battery was stored in a constant temperature bath at 85 ° C. for 24 hours. Thereafter, the ambient temperature of the battery was returned to 25 ° C., and discharged to 3.0 V at a constant current of 1.8 mA corresponding to 0.3 C. The maintenance rate was calculated by dividing the discharge capacity at this time by the initial capacity.

  Furthermore, after charging at a constant current of 6 mA corresponding to 1 C and the battery voltage reached 4.2 V, charging was performed at a constant voltage of 4.2 V for a total of 3 hours. Thereafter, the battery was discharged to 3.0 V with a constant current of 1.8 mA corresponding to 0.3 C. The recovery rate was calculated by dividing the discharge capacity at this time by the initial capacity.

(3) Measurement of lithium oxalate content Utilizing the fact that oxalate ions are generated when an organic lithium salt having an oxalate group is hydrolyzed, the total amount of oxalate group in the electrolyte is determined according to JIS K 8519. Quantified according to Next, in order to quantify the components of the organic lithium salt having an oxalate group other than lithium oxalate, an electrolyte was injected into a 3 mmφ NMR sample tube in an argon glove box. The sample tube was sealed using a Teflon (registered trademark) cap and a parafilm, and the electrolyte was sealed in an unexposed state. The 3mmφ NMR sample tube sealed with the electrolyte is inserted into the 5mmφ NMR sample tube into which the heavy solvent and the external standard are injected, and NMR measurement is performed by the double tube method, thereby quantifying the organolithium salt having an oxalate group. did. NMR measurement was performed by the single pulse method using ECS-400 manufactured by JEOL RESONANCE, and the pulse width was 45 °. The lithium oxalate content was calculated by subtracting the amount of oxalic acid groups corresponding to the organic lithium salt having an oxalic acid group from the total amount of oxalic acid groups.

[Example 1]
Under an inert atmosphere, a mixed solvent composed of 300 mL of ethylene carbonate and 700 mL of ethyl methyl carbonate was prepared as a non-aqueous solvent, and 1.0 mol of LiPF ₆ was dissolved in the mixed solvent to obtain an electrolytic solution (S11). It was. Next, 0.25 part by mass of LiB (C ₂ O ₄ ) ₂ and 0.1 part by mass of 1-methyl-1H-benzotriazole are added to and mixed with 100 parts by mass of the electrolytic solution (S11). As a result, an electrolytic solution (S12) was obtained. Incidentally, acetonitrile insoluble component _{LiB (C 2} O _{4) 2} used was 1.6 wt%, the FT-IR measurement, the acetonitrile insoluble component was confirmed to be the lithium oxalate. Subsequently, the lithium oxalate content was adjusted to 0 ppm by removing the precipitate of lithium oxalate from the electrolytic solution (S12) through decantation. In the ¹¹ B-NMR measurement, D ₂ O was used as the heavy solvent for the double tube, B (OH) ₃ was used as the external standard, and the number of integration was 1024 times. Combining the positive electrode (P1) and the negative electrode (N1) produced as described above, and the electrolyte solution (S12) that has undergone decantation, a coin-type non-aqueous secondary battery is manufactured according to the method described in (1-3) above. Produced. This coin-type non-aqueous secondary battery was subjected to a first charge / discharge treatment by the method described in (2-1) above, and a storage test was performed by the method described in (2-2) above.

[Comparative Example 1]
A coin-type non-aqueous secondary battery was produced in the same manner as in Example 1 except that (S11) prepared in Example 1 was used as the electrolytic solution. This coin-type non-aqueous secondary battery was subjected to a first charge / discharge treatment by the method described in (2-1) above, and a storage test was performed by the method described in (2-2) above.

[Comparative Example 2]
Under an inert atmosphere, 0.25 part by mass of LiB (C ₂ O ₄ ) ₂ was added to and mixed with 100 parts by mass of the electrolytic solution (S11) to obtain an electrolytic solution (S13).

  A coin-type non-aqueous secondary battery was produced in the same manner as in Example 1 except that the electrolytic solution (S13) was used. This coin-type non-aqueous secondary battery was subjected to a first charge / discharge treatment by the method described in (2-1) above, and a storage test was performed by the method described in (2-2) above.

[Comparative Example 3]
Under an inert atmosphere, 0.1 parts by mass of 1-methyl-1H-benzotriazole was added to and mixed with 100 parts by mass of the electrolyte (S11) to obtain an electrolyte (S14).

A coin-type non-aqueous secondary battery was produced in the same manner as in Example 1 except that the electrolytic solution (S14) was used. This coin-type non-aqueous secondary battery was subjected to a first charge / discharge treatment by the method described in (2-1) above, and a storage test was performed by the method described in (2-2) above.
The electrolytic solution compositions and evaluation results in Example 1 and Comparative Examples 1 to 3 are shown in Table 1 below.

Abbreviations in the non-aqueous solvent column of Table 1 have the following meanings, respectively.
EC: ethylene carbonate EMC: ethyl methyl carbonate LiBOB: LiB (C ₂ O ₄ ) ₂
MBTA: 1-methyl-1H-benzotriazole

From a comparison between Example 1 and Comparative Example 1, when an electrolytic solution containing LiB (C ₂ O ₄ ) ₂ and 1-methyl-1H-benzotriazole was used, the durability performance in the storage test was significantly improved. confirmed.

According to Comparative Example 2, when the non-aqueous solvent contains a significant amount of LiB (C ₂ O ₄ ) ₂ , a slight improvement in durability was observed in the storage test, but the result of Example 1 was far away. There wasn't. Further, according to Comparative Example 3, 1-methyl-1H-benzotriazole alone did not function as an additive at all, but it only became a factor of deteriorating initial efficiency. The results of Comparative Examples 2 and 3 reveal that the synergistic effect of LiB (C ₂ O ₄ ) ₂ and 1-methyl-1H-benzotriazole is unthinkable to those skilled in the art. It was.

  From the above results, it was verified that the non-aqueous secondary battery using the electrolytic solution of the present embodiment has achieved high durability performance.

  The non-aqueous secondary battery of the present invention is, for example, a portable device such as a mobile phone, a portable audio device, a personal computer, an IC (Integrated Circuit) tag; a rechargeable battery for a vehicle such as a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle; It can be applied to a residential power storage system.

DESCRIPTION OF SYMBOLS 100 Non-aqueous secondary battery 110 Battery exterior 120 Space of battery exterior 110 130 Positive electrode lead body 140 Negative electrode lead body 150 Positive electrode 160 Negative electrode 170 Separator

Claims (8)

A non-aqueous solvent,
An organic lithium salt having an oxalic acid group;
The following general formula (1):

{In Formula (1), R ¹ is an alkyl group having 1 to 4 carbon atoms, allyl group, propargyl group, phenyl group, benzyl group, pyridyl group, amino group, pyrrolidylmethyl group, trimethylsilyl group, nitrile group, acetyl group Group, trifluoroacetyl group, chloromethyl group, methoxymethyl group, isocyanomethyl group, methylsulfonyl group, phenylsulfonyl group, sulfonyl azide group, pyridylsulfonyl group, 2- (trimethylsilyl) ethoxycarbonyloxy group, bis ( N, N′-alkyl) aminomethyl group or bis (N, N′-alkyl) aminoethyl group, and R ² represents an alkyl group having 1 to 4 carbon atoms and a fluorine-substituted alkyl group having 1 to 4 carbon atoms. , An alkoxy group having 1 to 4 carbon atoms, a fluorine-substituted alkoxy group having 1 to 4 carbon atoms, a nitrile group, a nitro group, an amino group, or a halogen Is an atom, and k is an integer of 0-4. And a compound represented by:
A nonaqueous electrolytic solution, wherein the content of lithium oxalate is 0 to 500 ppm. The organic lithium salt having the oxalic acid group is at least one lithium salt selected from lithium salts represented by LiB (C ₂ O ₄ ) ₂ and LiBF ₂ (C ₂ O ₄ ). The non-aqueous electrolyte described. The non-aqueous electrolyte solution according to claim 1 or 2, wherein R ^{1 of the} compound represented by the general formula (1) is an alkyl group having 1 to 4 carbon atoms, and k is 0.   The non-aqueous electrolyte solution according to claim 1, wherein the non-aqueous solvent contains a cyclic carbonate.   The non-aqueous electrolyte solution according to any one of claims 1 to 4, wherein the non-aqueous solvent does not substantially contain acetonitrile.   Content of the compound represented by the said General formula (1) is 0.01-10 mass parts with respect to 100 mass parts of non-aqueous electrolyte solution, The non of any one of Claims 1-5 Aqueous electrolyte.   The method for producing a non-aqueous electrolyte solution according to any one of claims 1 to 6, wherein the lithium oxalate is removed by at least one method selected from decantation and filtration. A positive electrode having a positive electrode active material layer containing at least one transition metal element selected from Ni, Mn, and Co on one or both surfaces of a current collector;
A negative electrode having a negative electrode active material layer on one or both sides of the current collector, and
A non-aqueous secondary battery comprising the non-aqueous electrolyte solution according to claim 1.

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